Cover Crop Benefits and Drawbacks When Water is Scarce
This article was adapted from “Can cover crops improve soil ecosystem services in water-limited environments? A review” by Humberto Blanco-Canqui et al. First published in the Soil Science Society of America Journal on October 26, 2021.
The short answer: Cover crops can provide significant soil ecosystem services, even in drier environments. While lower main crop yields are a concern in particular instances, in most cases cover crops do not impact crop yields.
Dig deeper: Cover crops are likely to provide many ecosystem services in water-limited environments. These ecosystem services include:
- Reduced potential for wind erosion: Covering the top of the soil and holding on to soil with their roots
- Reduced potential for water erosion: Increasing what is called wet-aggregate stability, which helps the soil resist being washed away
- Reduced nitrate leaching and improved water quality: Taking up leftover nitrogen in the soil can mean less leaches into local waterways
- Weed suppression: Blocking light and taking other resources can reduce weeds and in some instances the need for herbicides in fallow fields
- Improved soil microbial communities: Improving the qualities of soil microbes can enhance the delivery of many soil ecosystem services
Beyond these ecosystem services, some studies have found success using cover crops as a forage to make them more economically viable.
- Combining haying and grazing might provide the most benefits long-term.
- A flexible strategy is needed to accommodate varying precipitation year-to-year because in low precipitation years, haying or grazing may need to be scaled back or skipped.
Break it down: When growing cover crops in water-limited regions, there are several management strategies that can increase the likelihood of success. A thoughtful approach can help ensure the cover crop does not take too much water from the soil.
- Seeding time: Seeding cover crops in the spring can help them become established in semiarid regions. This allows them to use water stored from winter and spring precipitation.
- Timely termination: Terminating cover crops as early as possible can help limit the risk of main crop yield reduction by lowering the cover crop’s opportunity to remove too much water from the soil.
- Species selection: Cover crop selection should take into account the specific environment, planting time, seed cost, and intended purpose. Generally, a single grass species, rather than a mix, is recommended because it can better outcompete weeds and provide the intended ecosystem services.
The big picture: In most cases, growing cover crops in arid regions does not increase nor decrease the sequence cash crop yield.
But it is important to note that there are some cases where the use of cover crops can decrease these yields.
- In years with low precipitation in particular, there is a greater likelihood that the use of cover crops can result in reduced main crop yields. More long-term data is also needed on this topic.
- In some environments, the benefits of ecosystem services can outweigh a slight decrease in yield.
In short, cover crops can provide valuable ecosystem services even in areas where water is scarce, although there is a small risk of lower main crop yields, particularly during low precipitation years. Specific management practices can reduce this risk.
Photo courtesy of USDA NRCS South Dakota.